Most manufacturers of phototypesetting machines place several fonts on one disc or film strip carrier with the entire disc or film strip being replaceable when it is desired to change fonts. It is known in the art that it is advantageous to separate a unitary disc into segments such as a number of pie-shaped disc portions so that each may be replaced on an individual basis upon the selection of a new font. Several manufacturers have employed such a segmental font system with the individual font segments being accurately located by expensive alignment pins and holes. However, since the mounting accuracy should be typically less than one mil, very little clearance exists between the holes and the guide pins which makes the segments difficult to replace and expensive to manufacture. Difficulty in replacement increases operator burdens and slows down such replacement.
Another approach is illustrated in U.S. Pat. No. 3,886,566 wherein the segments are seated against an inner arcuate portion and are cemented or screwed down against an outwardly extending shoulder portion. This approach is believed impracticable since high accuracy cannot be consistently maintained. It is also desirable to eliminate the use of screws or cement and provide for rapid, easy segment replacement.